Climate Change

Climate change means a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods (100 years).

Climate change is usually measured in major shifts in temperature, rainfall, snow, and wind patterns lasting decades or more.

Humans are creating climate change by burning large amounts of fossil fuels (coal, oil, natural gas), deforestation (when forests are cut down or burned, they can no longer store carbon, and the carbon is released to the atmosphere).

Greenhouse effect and Global Warming

A greenhouse is a structure whose roof and walls are made chiefly of transparent material, such as glass, in which plants requiring regulated climatic conditions are grown.

In a greenhouse, the incident solar radiation (the visible and adjacent portions of the infrared and ultraviolet ranges of the spectrum) passes through the glass roof and walls and is absorbed by the floor, earth, and contents, which become warmer and re-emit the energy as longer-wavelength infrared radiation (heat radiation).

Glass and other materials used for greenhouse wallsdo not transmit infrared radiation, so the infrared cannot escape via radiative transfer.

As the structure is not open to the atmosphere, heat also cannot escape via convection, so the temperature inside the greenhouse rises. This is known as the ‘greenhouse effect’.

Importance of Natural Greenhouse Effect

The green-house effect is a natural phenomenon and has been occurring for millions of years on the earth.

Life on the earth has been possible because of this natural greenhouse effect which is due to water vapour and small particles of water present in the atmosphere.

Together, these produce more than 95 percent of total greenhouse warming.

Average global temperatures are maintained at about 15°C due to natural greenhouse effect.

Without this phenomenon, average global temperatures might have been around –17°C and at such low temperature life would not be able to exist.

If greenhouse gases are not checked, by the turn of the century the temperature may rise by 5°C.

Scientists believe that this rise in temperature will lead to deleterious changes in the environment and resulting in odd climatic changes (e.g. increased incidence of El Nino), thus leading to increased melting of polar ice caps as well as of other places like the Himalayan snow caps.

Cryosphere: The cryosphere is the frozen water part of the Earth water system. Polar regions, snow caps of high mountain ranges are all part of cryosphere.

Over many years, this will result in a rise in sea level that can submerge many coastal areas and lead to loss of coastal areas and ecosystems like swamps and marshes (most important ecosystems from the point of ecological services), etc.

Carbon dioxide

Carbon dioxide is meteorologically a very important gas as it is transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation.

It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface. It is largely responsible for the greenhouse effect.

Its concentration is greater close to the earth’s surface as it is denser than air.

Ozone

Ozone is another important greenhouse gas. But it is in very small proportions at the surface.

Most of it is confined to the stratosphere where it absorbs the harmful UV radiation.

At ground level, pollutants like NO2 react with volatile organic compounds in the presence of sunlight to produce ozone (tropospheric ozone).

Water vapour

Water vapour is also a variable gas in the atmosphere, which decreases with altitude.

Water vapour also decreases from the equator towards the poles.

In the warm and wet tropics, it may account for four per cent of the air by volume, while in the dry and cold areas of desert and polar regions, it may be less than one per cent of the air.

One unique feature about this greenhouse gas is that it absorbs both incoming (a part of incoming) and outgoing solar radiation.

Methane

Methane is the most important greenhouse gas after carbon dioxide.

It is produced from decomposition of animal wastes and biological matter.

The emission of this gas can be restricted by using animal wastes and biological matter to produce gobar gas (methane).

Nitrous Oxide (N2O)

N2O or Nitrous Oxide is a greenhouse gas.

NO and NO2(nitric oxide or nitrogen oxide and nitrogen dioxide) emissions cause global cooling through the formation of (OH) radicals that destroy methane molecules, countering the effect of GHGs.

Carbon Monoxide

Carbon monoxide is a short-lived greenhouse gas (it is less dense than air).

It has an indirect radiative forcing effect by elevating concentrations of methane and tropospheric ozone through chemical reactions with other atmospheric constituents (e.g., the hydroxyl radical, OH.) that would otherwise destroy them.

Through natural processes in the atmosphere, it is eventually oxidized to carbon dioxide.

Fluorinated gases

Chlorofluorocarbons (CFCs)

CFCs were phased out via theMontreal Protocol due to their part in ozone depletion (explained in Geography > Climatology > Polar Vortex).

This anthropogenic compound is also a greenhouse gas, with a much higher potential to enhance the greenhouse effect than CO2.

Hydrofluorocarbons

Hydrofluorocarbons are used as refrigerants, aerosol propellants, solvents, and fire retardants.

These chemicals were developed as a replacement for chlorofluorocarbons (CFCs).

Unfortunately, HFCs are potent greenhouse gases with long atmospheric lifetimes.

Perfluorocarbons

Perfluorocarbons are compounds produced as a by-product in aluminium production and the manufacturing of semiconductors.

Like HFCs, PFCs generally have long atmospheric lifetimes and high global warming potential.

Sulphur hexafluoride

Sulphur hexafluoride is also a greenhouse gas.

Sulphur hexafluoride is used in magnesium processing and semiconductor manufacturing, as well as a tracer gas for leak detection.

Sulphur hexafluoride is used in electrical transmission equipment, including circuit breakers.

Black Carbon or Soot

Black carbon (BC) is a solid particle or aerosol (though not a gas) that contributes to warming of the atmosphere. Black carbon, commonly known as soot.

Soot is a form of particulate air pollutant, produced from incomplete combustion.

Black carbon warms the earth by absorbing heat in the atmosphere and by reducing albedo (the ability to reflect sunlight) when deposited on snow and ice.

BC is the strongest absorber of sunlight and heats the air directly.

In addition, it darkens snow packs and glaciers through deposition and leads to melting of ice and snow.

Regionally, BC disrupts cloudiness and monsoon rainfall.

Black carbon stays in the atmosphere for only several days to weeks.

Thus, the effects of BC on the atmospheric warming and glacier retreat disappear within months of reducing emissions.

Brown Carbon

Brown carbon is a ubiquitous and unidentified component of organic aerosol.

Biomass burning (possibly domestic wood burning) is shown to be a major source of brown carbon

Brown carbon is generally referred for greenhouse gases and black carbon for particles resulting from impure combustion, such as soot and dust.

Q. The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere, because it absorbs

the water vapour of the air and retains its heat.

the ultraviolet part of the solar radiation.

all the solar radiations.

the infrared part of the solar radiation

Among GHGs, only water vapor has the ability to absorb both incoming (UV) and outgoing (infrared) radiation.

Answer: d) the infrared part of the solar radiation (outgoing radiation).

GHG Protocol arose when World Resources Institute (WRI) and World Business Council for Sustainable Development (WBCSD) recognized the need for an international standard for corporate GHG accounting and reporting in the late 1990s.

Q4. What is ‘Greenhouse Gas Protocol’? (2016)

It is an international accounting tool for government and business leaders to understand, quantify and man-age greenhouse gas emissions

It is an initiative of the United Nations to offer financial incentives to developing countries to reduce green-house gas emissions and to adopt eco-friendly technologies

It is an inter-governmental agreement ratified by all the member countries of the United Nations to reduce greenhouse gas emissions to specified levels by the year 2022

It is one of the multilateral REDD+ initiatives hosted by the World Bank

Answer: a)

Global Warming Potential (GWP) & Lifetime of Green House Gases

Gas

GWP (100-year)

Lifetime (years)

Carbon dioxide

1

50-200

Methane

21

12

Nitrous oxide

310

120

Hydrofluorocarbons (HFCs)

140 -11,700

1-270

Perfluorocarbons (PFCs)

6,500-9,200

800-50,000

Sulphur hexafluoride (SF6)

23,900

3,200

Global Warming – Impacts

Melting of the ice caps

Melting of the ice caps and glaciers will lead to rise in sea level.

Thermal expansion also contributes to sea level rise.

Fertile agricultural lands on the coast will be submerged and saline water intrusions will degrade the neighbouring land. Ground water in such regions will become useless.

Populous cities lying on the coasts will be submerged under the sea.

Flooding in Himalayas and Ganga plains in wet season and drought in dry season will severely affect the country.

As a result of thawing of snow, the amount of arable land in high-latitude region is likely to increase by reduction of the amount of frozen lands.

At the same time arable land along the coast lines are bound to be reduced as a result of rising sea level and saline water inundations.

Extreme Climatic Events

Increased likelihood of extreme events such as heat wave, flooding, hurricanes, etc. will offset all the economic advancements made.

Biodiversity Loss

Loss of Plankton due to warming of seas will adversely affects marine food chain.

Bleaching of Coral Reefs (rain forests of the ocean) will cause great loss of marine biodiversity.

Rising temperature would increase fertilizer requirement for the same production targets and result in higher GHG emissions, ammonia volatilization and cost of crop production.

Rising temperatures will further affect the physical, chemical and biological properties of fresh water lakes and rivers, with adverse impacts on many individual fresh water species.

No Food Security

Climate Change affects crops by impacting irrigation, insolation as well as the prevalence of pests.

Increased frequencies of droughts, floods, storms and cyclones are likely to increase agricultural production variability.

Moderate warming (increase of 1 to 3°C in mean temperature) is expected to benefit crop yields in temperate regions, while in lower latitudes the crops will take a hit.

However, the natural calamities due to global warming can offset the benefits in temperature regions.

In coastal areas, sea level rise will exacerbate water resource constraints due to increased salinization of groundwater supplies.

Deterioration of Carbon sinks

High latitude forests store more carbon than tropical rainforests.

One third of the world’s soil-bound carbon is in taiga and tundra areas.

When the permafrost melts due to global warming, it releases carbon in the form of carbon dioxide and methane.

In the 1970s the tundra was a carbon sink, but today, it is a carbon source, all because of global warming. (global warming leads to more global warming).

Sea Level Change

Sea level change means the fluctuations in the mean sea level over a considerably long period of time.

Processes that cause Change in Sea Level

Eustatic changes occur when the volume of sea water changes due to factors such as

global warming and melting of ice sheets (rise in sea level) or ice ages (fall in sea level) and

changes in the volume of mid-oceanic ridges.

Tectonic changes occur due to a change in the level of land.

Isostatic changes take place due to addition or removal of load: during ice ages, landmass subsided due to the load exerted by the glacial ice. On the other hand, landmasses rise as the glacial ice is removed.

Epeirogenic movement occurs due to broad scale tilting of continents which may result in the rise of one part of the continent even as the other part may subside causing an apparent rise in sea level.

Orogenic movement (mountain building) results in the formation of lofty mountains and an apparent fall in sea level.

Importance of understanding Sea Level Changes

It provides key evidences regarding climate change in the past.

It helps in estimating the rates of tectonic upliftment in the past geological periods.

To assess the suitability of coastal locations for industrial and agricultural development.

To protect low-lying countries by building coastal dykes and embankments.

The task of mapping of areas likely to be affected by storm surges and periodic flooding becomes possible only if we know the likely areas to be affected by future sea level rise.

By identifying the areas of possible submergence in the near future it becomes possible to set up tidal power generation plants in suitable locations.

Changes in Global Sea Level

Short-Term

Short-term changes occur during a year.

Commonly, seasonal variations of 5-6 cm in sea level are observed in a year.

Short-term sea level change may be due to a complex interaction of the following factors:

Marine water density: Temperature and salinity control the density of sea water. Low temperature and high salinity produce high density of sea water and lower sea level.

Velocity of ocean currents: Fast-flowing ocean currents when taking a curved path cause a rise in sea level on their outer fringes.

Generally, a difference of 18 cm in sea level is observed between the two sides of a fast-flowing current.

Ice formation and fall in sea level: During winter the ocean water trapped in the icecaps of the northern and the southern hemispheres leads to a fall in sea level.

Piling up of water along windward coasts: A local rise of sea level occurs in the coastal region as water is driven towards the coasts by an air mass, for example, the sea level rises in south and east Asia during the monsoon months due to landward movement of the air mass.

The twentieth century has observed short-term global sea level rise due to the following factors.

Global warming in the last century due to anthropogenic activities has resulted in thermal expansion of ocean water. So, the sea level has risen by about 10 to 15 cm in the past 100 years.

Melting of ice-sheets in the Antarctica by about 3 per cent of its total volume of ice has, to some extent, contributed to global sea level rise.

In the last century, about 15 per cent of the total volume of the Greenland ice cap melted.

Besides these areas of ice-melt, other glaciers are also estimated to have contributed about 48 per cent of the global sea level rise.

Long-Term

Global sea level changes which exceed 100 m are possible only if the major ice-sheets melt or there are substantial changes in the volume of the world’s mid-oceanic ridge.

Impact of Sea Level Fall

A drop in sea level causes the death of coral reefs as the continental shelves on which they are formed are left dry. So, fresh coral reefs emerge along the fringe of dead corals.

In places of shallow continental shelves, the fall in sea level leads to greater aridity in the continental hinterland due to reduced surface runoff.

A fall in sea level in temperate and high latitude regions causes extension of ice caps and glacial tongues onto the continental shelves.

Impact of Possible Rise in Sea Level

Ice melt in the Antarctica may prove to be dangerous in the near future if the temperature of the atmosphere continues to increase.

A vast segment of the populated land, viz., the low-lying densely populated coastal areas, will be submerged. Even the small islands will be wiped out.

An estimated global population of about one billion will be affected by rise in sea levels.

Immense damage may be caused to the coastal structures like ports, industrial establishments, etc.

As a result of the rise in sea level, almost 33 per cent of the world’s crop lands could be submerged (coastal plains and deltas are made up of very fertile soils).

Accelerated coastal erosion may cause damage to and destruction of beaches, coastal dunes and bars.

As a consequence, a vast section of the coastal land will remain unprotected against the direct attack of sea waves.

Groundwater resources of the coastal regions will be severely affected by salinization due to marine water intrusion.

The ecosystem will suffer heavy damages as the deltas, coral atolls and reefs will be destroyed. New coral reefs on the outer fringe of the dead corals will be formed.

As a result of rise in sea level, the mouths of drainage basins will undergo submergence. This will lead to a readjustment of the long-profiles of the rivers, which are likely to show a rise.

Islands are the worst affected by the recent rise of sea level. Some of the affected islands are the Carteret Islands, located on the north-east of Papua New Guinea in the Pacific Ocean, and Tuvalu Islands, about 1000 km north of Fiji in the South Pacific.

To check the phenomenon of sea level rise that the ‘Oceans and Coastal Areas Programme Activity Centre’ was set up in 1987 under the aegis of the United Nations Environment Programme (UNEP) to identify the countries facing maximum risk of submergence.

Low-NOx (nitrogen oxides) burners reduce the creation of nitrogen oxides, a cause of ground-level ozone, by restricting oxygen and manipulating the combustion process.

India’s coal

Coal mined in India is a poor quality coal (India’s coal is not Carboniferous Coal. It is Gondwana coal) with less carbon, high ash (hard to dispose) and high moisture content (more gases; less fuel efficiency) .

To improve efficiency and reduce adverse effects, India should do away with its present sub-critical coal power plants and build more super-critical and ultra-super-critical ones (15-20% increase in efficiency).

Forests as carbon Sinks

When this biomass is buried the carbon is trapped forming a carbon sink.

When the carbon sink is exposed the biomass decomposes adding methane to the atmosphere and when the biomass is used as fuel (coal and petroleum) it releases CO2 back into the atmosphere (carbon source).

Ocean is also a very important carbo sink. Most of the carbon is trapped in the ocean and if a small fraction of this carbon is released the consequences will be disastrous.

In Canada’s boreal forests as much as 80% of the total carbon is stored in the soils as dead organic matter.

Tropical forests absorb about 18% of all carbon dioxide added by fossil fuels.

In the context of climate change, the most important carbon stores are the natural fossil fuel deposits.

This release of carbon from fossil fuel has caused greenhouse gas (GHG) concentrations in the atmosphere to soar to levels more than 30 per cent higher than at the beginning of the industrial revolution.

Because of this increase in atmospheric carbon, a lot of emphasis and hope has been put into the ability of trees, other plants and the soil to temporarily sink the carbon that fossil fuel burning releases into the atmosphere.

Indeed, the Kyoto Protocol, the international communities’ main instrument for halting global warming suggests that the absorption of carbon dioxide by trees and the soil is just as valid a means to achieve emission reduction commitments as cutting carbon dioxide emissions from fossil fuels.

Q. The scientific view is that the increase in global temperature should not exceed 2 °C above pre-industrial level. If the global temperature increases beyond 3°C above the pre-industrial level, what can be its possible impact/impacts on the world?

Terrestrial biosphere tends toward a net carbon source

Widespread coral mortality will occur.

All the global wetlands will permanently disappear.

Cultivation of cereals will not be possible anywhere in the world.

Select the correct answer using the code given below.

1 only

1 and 2 only

2, 3 and 4 only

1, 2, 3 and 4

Explanation:

Taiga and temperate forests act as an important carbon sink. Global warming by 3 °C will turn these forests into carbon source.

Corals are very sensitive to temperature changes. 3 °C rise in global temperature will lead to widespread coral mortality.

3° C rise in global temperature will lead to submergence of many low lying coastal wetlands due to rise in sea levels. Inland wetlands like Keoladeo Ghana National Park will not be affected.

It has been estimated that a sea-level rise of approximately 2.3 metres (7.5 ft) for each degree Celsius of temperature ca occur within the next 2,000 years. (http://goo.gl/LH3RMl)

Cultivation of cereals in tropics will take a hit. But in temperate regions their production increases in the short run.